Building a 15 " OS waveguide, with paper mache and 3d printing

[Tarkovsky]

Hi everyone,

Like a lot of people on here I'm very interested in building my own OS waveguide. TBH, I'd probably settle for a ready made product, but they seem to be very hard to get hold of, and I enjoy learning about this kind of thing.

My general plan was this, design a mold for the waveguide in sketchup, get it 3d printed, apply paper mache, voila.
Am I being ridiculously simplistic here? I haven't seen anyone use 3d printing before. Is there a major issue with this or is it just quite new and untested tech for this application?

Obviously I have to get the shape of the mould perfect, and the paper mache itself to the right consistency to create an extremely smooth surface.
TBO I have seem a few of the spreadsheets for building the waveguide, and I'm a little bewildered, but I guess that's just part of the fun right?

To put the project in context, this is for a home hifi in a relatively small room. I'll also be building some kind of mid horn to match the the waveguide, and then later add subs.

Thanks a lot!

Zak

 

[boris81]

I don't think there will be a problem printing the waveguide itself. There are many web services that will 3D print an object of your design and ship it to you at a reasonable price. There are many materials to chose from, some of the most common are plastic, ceramic and metal.

I've never done anything of the sort but I guess the bulk of the work would be measuring and tweaking the prototypes until you come up with the end design. You will probably have to go through a few iterations before you get perfect results.

This is a good place to start with some theory.
Practical DIY Waveguides - Part 1

 

[boris81]

Oh wait, I missed the 15" part. That's probably larger than what commercial 3D printing services will do.

 

[wesayso]

Look here: 3D Printing Materials on Shapeways
for examples of material properties and the size you can print.
Don't count on it to be cheap though in those big sizes...

 

[kevinh]

John Inlow who has posted here has a nice description of his Paper horn. His is a Tractrix horn, and not an OS waveguide. His description of the process should be helpful.

I would think that a 15" OS waveguide would work well in a 2 way system (Like E Geddes did in his Summa design.

Hope this helps.

 

[wesayso]

I have only printed in black strong and flexible but it was usable as end product for me:

Tweeter housing is a 3D model I made and printed at Shapeways. Very strong PA nylon material. If I'd need a small waveguide for a tweeter I wouldn't hesitate and use 3D printing but a 15" waveguide? Not so sure...
My model is hollow to save cost, filled with CLD material (Butyl + aluminium) for car doors etc.

(this one was for a different tweeter but the same idea)

I've had printed RVS models in my hands, but they get expensive fast. Great for making small reasonably strong parts that are otherwise not available.

 

[dumptruck]

Probably makes more sense for the mounting plate/entrance, but precision CNC probably makes more sense for less money there. Might have to wait another decade for printing to be a reasonable option for a whole waveguide. Don't get me wrong, I'm all for impractical DIY if the person doing it doesn't care if the cost/time/results ratio makes sense.